The Japan Transport Safety Board (JTSB) was established by integrating the Japan Marine Accident Inquiry Agency (JMAIA) and the Aircraft and Railway Accidents Investigation Commission (ARAIC) on 1 October 2008, in order to enhance and combine investigation capacities for dealing with the causes of aircraft, marine and railway accidents/incidents and to prevent their recurrences. This integration resulted in the Japan Transport Safety Board carrying out investigations into the causes of air, marine and rail accidents and the Japan Marine Accident Tribunal taking disciplinary actions against licenses of seafarers. This article gives the background to the reorganization and overviews of the new entities.